What Causes Headaches In Child After Waking Up Or While Standing?

My son has headache in past 2 days. Both days it started right after he woke up. Yesterday was a mild pain so he was at school ad was fine by noon. Today he is in pain only when he stands. As soon as he stands up he has headache. He has similar symptoms in January and February (for 2 days) and feeling of nasal congestion, but no runny nose nor mucus present